The present invention relates to power control switches and, more particularly, to two terminal switches which may be turned off remotely.
Prior to the present energy crisis, it was more cost effective to waste inexpensive electricity purchased at bulk rates, than have individual switches installed in offices of large buildings, industrial plants, or other facilities. However, because of the present high cost of electricity, and the national need to conserve energy, it is now desirable to provide for more efficient use of electricity in such applications.
Present practice in many large buildings is to have a main circuit breaker to control the lighting to a number of individual offices, without a separate light switch in each office. This practice is both inconvenient and highly inefficient.
Thus, not only is there a need for separate light switches which allow for turn-on and turn-off of individual office lights, but also a light switch which provides for remote turn-off of all lights while retaining individual turn-on and turn-off capability.
Existing three and four terminal solid state switches, which may be remotely controlled, are suitable in many applications. However, they do require either a third wire from the AC line or an external control line, either of which are disadvantageous in other applications. Also, these three and four terminal switches use half cycle zero voltage crossing circuits to gate a triac on. Such configurations, when used with inductive loads, such as fluorescent lights, for example, create undesirable radio frequency interference (RFI) type signals. Additionally, present two terminal switches, such as commercially available solid state dimmer switches, are phase control circuits designed for use with incandescent lamps only, and cannot be remotely controlled.